1. Field of the Invention
This invention will allow for the replacement of previously used motor fuels including gasoline and diesel fuel, in order to improve the quality of the environment. In particular this invention relates to an apparatus for storing natural gas (i.e., gas compositions which are constituted primarily of methane but which may contain minor amounts of other components such as ethane, propane, I-butane, N-butane and/or nitrogen) in hydrate form and to a method of using the apparatus to provide for safe and clean automotive use of a practical alternative fuel.
2. Discussion of the Background
The search for alternative transportation fuels has expanded in recent years. The need for alternative fuels to replace gasoline has been accelerated by environmental concerns, concerns of shortage of imported liquid hydrocarbon, and Congressional prompting. The environmental concerns stem from the fact that gasoline combustion emits nitrogen oxides, particulates, carbon monoxide, and hydrocarbons that cause air pollution. The U.S. consumption of crude oil processed for gasoline was 7.15 million barrels per day in 1991. The first conversions from gasoline to compressed natural gas are occurring with fleet vehicles where 30,000 were in service in the U.S. in 1991 with the number expected to grow 80,000 by the year 2000. Furthermore, proposed legislation such as the Federal 1990 Clean Air Act amendments demonstrates the great need for conversion to alternative fuels in the United States.
Natural gas is the cleanest burning fossil fuel. This feature has stimulated interest in natural gas as an alternative to gasoline for fueling automobiles. Natural gas has an octane number of 120, burns with no particulate matter emitted, and emits one-third less carbon dioxide than gasoline. Further, compared to other fossil fuels, compressed natural gas has the highest energy content per unit weight but the lowest energy content per unit volume. But the means of maximizing natural gas on-board in a practical and safe manner has been difficult. Storage as a hydrate offers added safety, greater storage capacity, lower pressures, and cheaper storage.
Although gas storage of hydrates has been suggested, no mention has been made prior to this invention of on-board vehicle storage of hydrates. Previous publications on the possible non-vehicular storage of hydrates evaluate the use of hydrate storage of natural gas in permafrost regions and beneath the ocean floor to meet daily and seasonal variations of gas consumption. A few patents have also been granted on the bulk storage of hydrates. However, none of the structures in these references is suitable for storing hydrates on a land-based vehicle.
Other references discuss natural gas-powered vehicles in which the natural gas is stored at a reduced pressure by using a sorbent material introduced into the gas storage tank. However, these references do not employ gas hydrates.
Therefore, the need for safe storage of adequate quantities of natural gas on vehicles and a method for use of the natural gas in vehicles is growing.